Liquid addition product of an acetal and dialkyl esters of an alpha-beta unsaturatedaliphatic dicarboxylic acid as an antifoaming agent for hydrocarbon oils



Patented Sept. 15, 1953 N LIQUID ADDITION PRODUCT OF AN `ACETAL AND DIALKYL ESTERS OF AN ALPHA-BETAV UNSATURATED ALIPHATIC f DICARBOXYL- IC ACID AS AN ANTIFOAMING AGENT FORi HYDROCARBONJOILS i Joseph E.` Fields,` Dayton,` Ohio, assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation' of Delaware No Drawing. Application November-273.1950,r Serial No. 197,837` i `3 Claims.

invention relates to antifoaming hydrocarbon oils andldeals'more particularly withhy.-

drocarbon oils containing as antifoaming agents, smalle-amounts of certain ketonic esters.

corrosive lubricants, for lubricants of increased viscosity .and low-pour-point and good detersive properties have been met by the formulation and use of numerous chemicals which givethese The problem of foaminhibitin is one of ma- 5 desirable properties to oils when admixed therejor importancer to allindustries employing hywith, the use of such' additives makes theA treat- -drocarbonloils under` 'foam-inducing conditions. ed oils particularly susceptible to foaming. While most 4oils willfoam to some extent due to While light grade oils, e; g. SAE 1'0 grade oils, vigorous agitation and,` aeration in a running enare almost non-foaming under the most severe gine;` foaming becomes a problem` only when conditions, when there"-,are employed with these loss` of oil occurs by, foam seepage or when so oils one or more additives such as viscosity inmanyair bubbles are present in the oil that dex* 'improvers extremei pressure resisting improper lubrication .of bearing surfaces is improvers, pour-point' depressors,etc., the resultpeded. Foaming `is oftenexperienced with dry ing? improved oils do not :retain their nonsumpk enginesin which thereis employed a scavfoaming characteristics and` are frequently even enger pump for collecting oilfrom various enmore susceptible `itoffoaminglthanare rthe heavy gine partsv and returning it to the lubricantresgrade oils; l i ervoir. Here air may be collected along with Hence, with lthe `developnrient of` `new highthe oil and deposited in the reservoir. The despeed enginesandi-the provisionof the new adsign .and operation of aircraft engines is such that foaming occurs more readily in this `type Aof engine than it does in automotive engines.

Foam `andfroth in hydrocarbon oils, however, is not due solelyfto engine design although location and design of the oil pump, oil sump and oil lines as wellas modification of other me-` chanical y features may` retard foam development;

when certain 4oils are employed with high speed engines, mechanical control, alone, does not sufllore.` Here, thenature of the lcrankcase oil is oftenthe prime 'factorinfoaming difficulties, The heavier thegrade offthe oil or. the higher .theviscosity offthe oil, themore dificultfit ,is to avoidfoaming. Heavy grade `oils,` such as those employedin high-speed dieseland spark ignition engines operatingunder lsevere conditions are particularly :susceptible to foaming. The heavy oils hold bubbles very firmly so that when foamrisiformed, .it is very persistent.

, Newrdevelopments in` engine construction have `constantly demanded lubricantshaving properties not possessed by crude hydrocarbon oils. Such properties are now generally impartedto lubricants by the useof additives. For example, in order ,to satisfythe lubrication requirements of hypoid gears, materials which impart ex- `:treme-pressure resistingproperties are now generally added to gear` lubricants. In most cases. however, they improvement Iattained in oils b y the use of additives is made only 'at the expense of increasing-its susceptibility to foam. Thus, while\thedemands `of modern engine design for .extremer-pressure resisting lubricants, for anti.`

.ditive-type"lubricants; the problem of foaming has assumed major importance. Attempts to solve-theproblem by -defoaming existing oils, e. g., by submitting lo'ils to heat-treatment, absorption :processen `filtering steps, etc., have proved of but little value. The most practical solution to this proble'mhas been made by the use of antifoam additives;

A number of antlfoam additives; `iii-e., antifoaming agents; foam-depressing agents, foam depressants, antifrothers or foam suppressors, are known; but in thepr'ior artf their-'use has been attended lwith vnumerous diculties. Among disadvantages orsi-ich 'known additives are chemical reactivitywith the lubricant or other oil additives, corrosive effect, susceptibility to decomposition upon heating, instability when exposedforlong periodsofltimeto ordinary atmospheric conditions, high cost, etc.

Now I have found that' foaming` of hydrocarbon oils is efliciently retarded" and even completely inhibited when'theiteis addedto such oils a small quantity, sayj, from" 02001r percent to 1.0 per cent b y weight oi."l a liquidaddition product of one mole of anacetal with from 2 to 20 moles of certain dialkyl estersofan alpha-beta unsaturated aliphatic dicarboxylic acid of not more than 6carbon*atornslA Addition products of this kind aredescribed 'in the" copending application of Tracy MLPatrick; Serial No. 197,829, led of even date." They arereadily obtained by contacting anacetal"h`aving the general formula shown below with th'ed'ialkyl `dicarboxylate in the presence cfa freeradical ,liberating agent and maintaining the resulting mixture at ordinary or increased temperatures until formation of -a liquid mixture of addition products has been formed and separating any unreacted malauroyl peroxide, lstearoyl peroxide, hydrogenV peroxide, peracetic acid, sodium perborate, potassium persulfate and the like. Instead of the peroxidic catlyst, ultra-violet radiation may be employed.

.Acetals yemployed for the preparation of the present liquid addition product have the general formula wherein R is selected from the group consisting of hydrogen, alkyl, cycloalkyl and aralkyl radicals, and R and 'R" are saturated hydrocarbon radicals. Preferably R is an alkyl radical containing up'to 7 carbon atoms. R' and R preferably contain up to '7 carbon atoms and more preferably are identical alkyl radicals.

` The term saturated" as used herein excepts normal benzene ring unsaturation since benzene does not give any' rea-ction with bromine waterand practically all of its reactions are those of substitution instead of addition. "f Illustrative acetals are, for example,

I Dimethoxymethane Diethoxymethane 1,1-dimethoxyethane Acetal (1,1-diethoxyethane) 1,1-diethoxybutane 1,1-diethoxyheptane 1,1-dipropoxyhepthane 1,1-dibutoxyethane 1,1- (di-2-ethylhexoxy) butane 1,1-didodecoxydodecane l-methoxy-l-ethoxyethane l-propoxy-l-butoxybutane 1,l-dicyclopropoxyheptane 1,'1-dicyclohexoxybutane 1,1-dibenzoyloxyethane 1,1-diphenethoxybutane 1,1-diphenoxyheptane 1,1-ditolyloxybutane 1-ethoxy-l-cyclohexoxypropane 1-benzoyloxy-l-phenoxyhexane 1cyclopropoxy-l-tolyloxypentane 1-ethoxy-l-phenethoxyethane Diethoxycyclohexylmethane Dibutoxycyclopropylmethane 1,1-dimethoxy-2-phenylethane 1,1-dipropoxy-Z-tolylethane and the like Dialkyl a-aliphatic olenic dicarboxylates Each -adduct contains only one mole of i the acetal, but the number of moles of ester used for the preparation of the present antifoaming agents have the general formula in which Y and Z are selected from the class consisting of hydrogen and the methyl radical and X is an alkyl radical of from 1 to 8 carbon atoms. Examples of useful dialkyl carboxylates having the abovegeneral formula are dimethyl, diethyl, di-n-butyl, diisobutyl, di-tert-butyl, din-amyl, diisoarnyl, di-tert-amyl, dihexyl, diisohexyl, di-in-heptyl, and di-n-octyl, maleates, fumarates, citraconates and mesaconates.

lThe present liquid addition products may be represented by the formula in which R is selected from the class consisting of hydrogen, alkyl, cycloalkyl and aralkyl radicals, R' and R are saturated hydrocarbon radicals, Y and Z are selected from the class consisting of hydrogen and the methyl radical, X is an alkyl radical of from 1 to 8 carbon atoms and n is an integer of from 2 to 20.

The present acetal-ester adducts are effective antifoaming agents When they are employed in very low proportions, i. e., in amounts of up to 1.0 per cent by Weight, based on the weight of the total hydrocarbon oil composition. From 0.01 per cent to 0.5 per cent of the adducts is preferred, depending upon the nature of the oil. Heavy oils and oils containing foam-inducing adjuvants require more of the present antifoaming adducts than do base oils ofgood viscosity characteristics.

The antifoaming effect of the acetal-ester adducts is not materially affected bythe presence of other adjuvants in the oil. Thev present adducts are stable materials which can be-` hydrolyzed only with difficulty, and since they are present in the oils in only very small quantities, the use of even. Very acidic or very basic addi-O tions in the oil has substantially no efect on the adducts. vHydrocarbon oils containing the present avntifoaming agents are stable when stored over long periods of time and also when subjected to heat and pressure conditions of engine and motor operation.

While the antifoaming effect of the acetalester adducts is obtained when they areemployed in concentrations of up to 1.0% by Weight, the adducts may be incorporated into hydrocarbon oils of much higher proportions, e. g., in amounts of up to 10 per cent or even 50 percent of the weight of the hydrocarbon oil tc give concentrates. `Oils containing such high proportions of the adducts may be manufactured and sold for use as lubricant additives. Addition of small amounts of such concentrate to hydrocarbon oils may be made so as to supply an oil containing suitable quantities of the adducts.

Hydrocarbon oils which are rendered substantially antifoarning by incorporation therein of quantities of up to 1.0 per cent of the present adducts are synthetic or petroleum stocks of varying viscosities such as lubricating oils for internal combustion engines and motors, diesel fuels and lubricants and pressure transfer media, e. g., industrial lubricants, process oils, hydraulic oils, turbine oils, cutting oils, fluid greases, gear oils, shock absorber oils, spindle oils, journal bearing oils, pneumatic tool lubricants, etc. They may be synthetic or natural hydrocarbons of any type, i. e., paralinic, naphthenic or blended.

The invention is further illustrated, but not limited, by the following example.

Example The antifoaming properties of lubricants may be determined according to the procedure generally described in Designation L-12-445 of the C0- ordinating Research Council, New York. Briefly this procedure involves bubbling air or an inert gas such as nitrogen through the hydrocarbon oil to be tested, employing standard apparatus and standard conditions.

The oil was placed in a standard U-ml. graduated ycylinder in the top of which was inserted a two-hole rubber stopper. An air-inlet tube extended through this stopper, to the bottom of which was attached a gas diiuser or porous stone sphere. The length of the inlet tube was adjusted so that when the apparatus was assembled, the sphere just touched the bottom of the cylinder. The sphere was attached to the inlet tube bymeans of litharge or glycerine, or by a copper tube soldered to the diiTuser-stone coupling. The oil bath used was capable of controlling temperature at 200i10 F. (93.3i0.6 C.), large enough to permit the cylinder to be immersed at least to the 90-ml. mark, and arranged to permit the visual observation of the graduations on the cylinder.

Dry nitrogen or air was supplied at the rate of 0.2 cubic foot per hour, employing a calibrated owmeter. The sample was heated to 120 F. (48.9 C.), and then cooled, before testing, to 75 i 5 F. (23.9 i 2.8 C.) in a constant temperature room. ce. of oil `was used for each test.

With the air hose disconnected between the flowmeter and the delivery tube to the diffuser stone, the stone was allowed to soak in the oil for 5 minutes, at the end of which time the air ilow (0.2 cu. it. per hour) was started through the stone. Zero time was noted when the air or nitrogen bubbles started to rise from the stone. Readings of the top and bottom foam levels were taken at the end of a 5-rninute period. The volume of foam was calculated from the two readings.

Employing the testing procedure described above there was determined the antifoaming effect of a liquid mixture of acetal-diethyl maleate adducts when added to a Champlin SAE base oil in concentrations of from 0.02% to 0.05% by weight of the oil. The liquid mixture of adducts, B. P. above 200 C./0.6 mm. 111325 1.4558 consisted of adducts of one mole of acetal with from 2 to 20 moles of diethyl maleate and was prepared by reuxing one mole of acetal (Ll-diethoxyethane) with 0.25 mole of diethyl maleate for 42 hours in the presence of a mixed free-radical promoting catalyst consisting of 1.0 cc. of tertbutyl peroxide and 1.5 g. of benzoyl peroxide, and separating from the resulting reaction mixture material boiling below the above-stated boiling point, as described in the previously cited cepending application.

The following results were obtained:

In the absence of an additive, the Chaniplin 30 SAE oil gave '71 cc. of foam under the same testing conditions.

Nonfoaming hydrocarbon oil compositions may be obtained by incorporating into such oils in a quantity of up to 1.0% based on the weight of the composition, other liquid mixtures of adducts of one mole of one of the present acetals with from 2 to 20 moles of the unsaturated di carboxylates. Thus, instead of the acetal-diethyl maleate adducts employed in the above example there may be used, e. g., adducts of one mole of dimethoxymethane, of 1,l-(di2ethylhexoxy)- butane, of 1,1-dicyc1ohexoxybutane and of 1,1- diphenoxyheptane with from 2 to 20 moles of an ester such as di-n-butyl fumarate, diisoamyl mesaconate or di-n-octyl citraconate. The present adducts impart antifoaming properties to hydrocarbon oils, and may be used in the presence of other customarily employed additives such as extreme-pressure resisting additives, detergent additives, etc.

What I claim is:

1. A lubricant composition containing a hydrocarbon oil and up to 1.0 per cent by weight based on the weight of the composition of a liquid mixture of adducts having the formula in which Y and Z are selected from the class consisting of hydrogen and the methyl radical and X is an alkyl radical of from 1 to 8 carbon in which X is an alkyl radical of from 1 to 8 carbon atoms and n is an integer of from 2 to 20.

3. A lubricant composition containing a hydrocarbon oil and up to 1.0 per cent by weight based on the weight of the composition of a liquid mixture of adducts having the formula CHaCHz--O H in which n is an integer of from 2 to 20.

JOSEPH E. FIELDS.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,380,304 Gleason July 10, 1945 2,528,466 Borsoff Oct. 31, 1950 2,528,465 Borsoni Oct. 31, 1950 2,570,788 Giammaria. Oct. 9, 1951 OTHER REFERENCES Foaming of Aircraft-Engine Oils as a Problem in Colloid Chemistry, NACA Report ARR No. 4105, 1944, by McBain et al. 

1. A LUBRICANT COMPOSITION CONTAINING A HYDROCARBON OIL AND UP TO 1.0 PER CENT BY WEIGHT BASED ON THE WEIGHT OF THE COMPOSITION OF A LIQUID MIXTURE OF ADDUCTS HAVING THE FORMULA 